Duration-rainfall intensity equations: Study of IDF curves using local precipitation data

One significant parameter required when designing hydraulic structures is the intensity of the storm for a selected return period. The rainfall intensity can be read off graphs called rainfall intensity-duration-frequency (IDF) curves when they are available. The construction of IDF curves requires continuous records of annual storms. Unfortunately, continuous precipitation data is not always available. To generate IDF curves in places where continuous records are not available, David C. Froehlich, proposed a method to determine the IDF equations for any duration between 1 to 24 hours using precipitation values from the National Weather Service (NWS) Isopluvial maps.; Based on Froehlich's approach and using the Gumbel distribution, the aim of the present work is to develop a methodology to determine statistical parameters required to describe rainfall intensity using only the 24-hour rainfall records that are available in most areas. The results will be able to relate the annual maximum series rainfall depths to the desired return period by plotting the IDF curves for various durations and return periods. The methodology proposed will be tested using actual data obtained from the Carbondale area and the results will be compared to the method devised by David C. Froehlich.